Water-resistant paper or paper-board product and process of making the same



Patented July 29, 1930 UNITED STATES PATENT OFFICE ALBERT L. OLAPP, OF DANVERS, MASSACHUSETTS, ASSIGNOR TO THE FLINTKOTE COM- ]?ANY OI BOSTON, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS WATER-RESISTANT PAPER OB PAPER-BOARD PRODUCT AND IRO'CESS OF MAKING THE SAME No Drawing. Application filed June 9,

This invention relates primarily to the production of a Water-resistant paper or paper board products, permeated uniformly throughout with a large proportion of unsaponified thermoplastic waterproofing material fused onto the fibers thereof, together with an insoluble soap sizing agent which assists in imparting Water resistance to the paper product. More specifically, the paper product herein contemplated contains as the unsaponified waterproofing material an asphaltic body, and as the soap sizing agent an insoluble rosin soap, together with a certain amount of free or unsaponified rosin.

In accordance with this invention, an aqueous rosin-soap-asphalt dispersion is prepared by heating and liquefying the asphalt, and then gradually and progressively adding the liquefied asphalt with agitation to a heated aqueous solution of the rosin soap or ros1n soap-forming constituents, untll as h gh a concentration of dispersed asphalt as is consistent with the production of a stable and non-sticky dispersion has been attained therein. The resulting dispersion contains a high proportion of unsaponified thermoplastic material in the form of dispersed particles of asphalt, i. e., in the internal or disperse phase, stabilized by the rosin soap solution which constitutes the external or continuous phase of the dispersion.

The dispersion is incorporated into papermaking fibrous stock in the beater engine, together With sufficient water to ensure circulation, and is uniformly disseminated throughout the stock by the operation of the engine. A suitable precipitant, such as alum or aluminum sulphate, is added to the stock, thus breaking down the dispersion by producing an aluminum resinate precipitate, which carries down therewith and fixes the unsaponified, 'dispersed asphalt particles on the fibres. The fibrous stock is then formed into paper on a papermaking machine, e. g., a Fourdrinier machine, equipped with dryers and hot calenders. During the drying and calendering operations, the particles of asphalthaving a melting point varying from to 240 F.,'dependmg upon the variety of asphalt employedare fused or melted,

1926. Serial No. 114,869.

resulting in a fusion and coalescence of the particles within the sheet and in a uniform permeation or saturation of the sheet. In

other Words, the asphalt becomes fused onto and envelops or Waterproofs the individual fibers, so that the paper is highly resistant to the action of moisture or water.

Inasmuch as only a limited and relatively proofing material and consequently are not highly resistant to the action of water. In addition, precipitated aluminum resinate is not freely fusible at the temperature at which paper is dried or calendered, and the size functions more as a Water repellent medium by virtue of its surface tension against water, rather than exercising a positive protecting action as a continuous film of waterproofing material fused onto the individual fibers. This latter condition prevails in the present invention in which the asphalt, unaltered chemically by the dispersing and fixing process, retains its-normal adhesiveness and fusibility after removal of the 'water from the sheet.

By the practice of the present invention, however, a very high proportion of waterproofing or sizing material, containing, say, 10% to 40% asphalt, based on the dry weight of fibrous, stock, may be successfully incorporated into paper, and is present therein essentially in unsaponified condition, the precipitated insoluble soap component thereof being formed from rosin soap present in the dispersion in amount only sufficient to permit an effective dispersion of the preponderant unsaponified asphalt-ic component. Moreover, a paper product produced as herein described is more highly water-resistant than paper which contains an equal amount of sizing material essentially Wholly in the form of a metallic, insoluble soap precipitated on the fibers, such soap having a lower waterproofing capacity and possessing a fusing or melting point considerably above the temperature maintained at the dry end of a paper machine. p

A specific example of procedure which may be employed in preparing a dispersion su1table for use in producing a highly waterproof paper product may be substantially as follows. The .rosin soap solution to be employed as the dispersing agent and preferably containing free or unsaponified rosin may be produced by any suitable method. For example, 100 parts of rosin (gum or wood) may be heated and melted and then mixed together with a solution of a suitable saponifying compound of sodium, say, sodium carbonate, about 12 parts of sodium carbonate being suflicient to produce the desired amount of soap component. The materials are then cooked together with agitation, additional water being added from time to time. for a sufficient period of time to effect saponification, i. e., until the sodium carbonate has largely been consumed. Saponification requires about eight to twelve hours, the resulting size containing about to parts of free rosin and 20 to 30 parts of rosin soap or sodium resinate, with more or less free alkali. A rosin soap solution thus prepared is suitable as the dispersing agent for the asphalt. 1

The asphalt employed as the waterproofing agent may be of any suitable variety, depending on the characteristics which it is desired to impart to the finished paper. For example, a natural low melting asphalt of a melting point of, say, 100 F., or an oxidized or blown asphalt having tough, rubbery characteristics and a meltingpoint of about 240 F., may be utilized, or any other natural or artificial asphalt within this range of melting points.

The asphalt is heated until it becomes highly fluid prior to effecting its dispersion. If desired, a softening or tempering agent, such as a mineral oil, may be added thereto, especially when the asphalt is of high melting point. The asphalt is then gradually and progressively added, with agitation, to the solution of rosin size diluted to the desired degree and heated to a boilingtemperature, or approximately 212 F. The addition of the liquefied asphalt With agitation results in the resolution or dispersion thereof into fine, discrete particles of ultra-fine or colloidal size, the solution of sodium resinate functioning as the dispersing agent and protecting or enveloping the dispersed particles as they are formed, so that there is little, if any, tendency forthe particles to agglomerate or coalesce while they are in heated condition or after they are cooled and congealed. The progressive addition of the asphalt is continued until as large a proportion of asphalt has been added as is consistent with the production of a stable and nonadhesive dispersion,-about to 85 parts of asphalt and 15 to 40 parts of rosin (based on initial dry weight of unsaponified rosin) resulting in a stable, non-adhesive dispersion which may be diluted with water to an desired consistency without material su sidence of the dispersed particles. It is obvious that these proportions may be varied, depending upon the nature of the asphalt and the result which it is desired to accomplish. Certain boards, for instance, may be made with hard asphalt, whereas other boards may be made with softer material. \Vhere hard and less sticky asphalt is used, generally less sodium resinate may be em-' ployed to produce a dispersion which is capable of being run on a paper machine. Where, on the other hand, a softer and more adhesive asphalt is employed, a larger amount of rosin soap is required to stabilize the dispersion sufficiently so that the original stickiness of the soft asphalt may be adequately overcome to avoid a gumming of the instrumentalities of the paper machine. Generally, dispersions of the proper consistency may be determined by manual manipulation. Thus, if the dispersed prodnot as it comes from the dispersing device, when handled between the fingers, is slip pery and cannot be pressed out into coherent particles, the dispersion is considered sufficiently stable to operate satisfactorily. Furthermore, after the stock has been mixed with the dispersion and treated with alum, when squeezed and drained between the hands, it should exhibit no signs of stickiness and the water should drain away from the stock free and clear from any substantial quantities of dispersion. In the event that the dispersion does not answer the above desiderata, either the asphalt should be hardened or the amount of rosin soap increased, or additional protective elements added to the stock in the form of silicate of soda or inert colloidal solids.

Any other suitable method of procedure I for bringing together and mixing the components of the dispersion may be employed. For example, the asphalt may be continuously dispersed by passing continuous streams of rosin size and liquefied asphalt, each supplied at predetermined rate relative to each other, through a centrifugal pump. Or dry rosin size containing the desired soap and free rosin content and asphalt may be melted together in the desired proportion, and the mixture may be atomized and discharged into a body of Water by an Erfurt machine. Moreover, the steps may be somewhat modified. For example, the asphalt, when of sufficiently low melting point or tempered to produce an asphalt of sufliciently low melting point by a suitable softening agent, may be heated and rendered fluid in an aqueous solution of rosin the fact that the agitation must be continued for a prolonged period, that is, during the sapomfication reaction of the IOSll'l soapformlng constituents, and may be accompanied by undue foaming.

The dispersion, preferably cooled'with such dilution with water as may be desired, is added to paper-making fibrous stock in the beater engine, together with sufiicient water to ensure the circulation of the mass, whereupon the beater roll is set in operation and the dispersion is uniformly disseminated throughout the mass. About to of asphalt, depending upon the character of the paper product which it is desired to produce, based on the dry weight of fibrous material, may be successfully added to the stock in the beater. The fibrous stock may comprise various cellulosic fibers, such as mechanical or chemical wood pulp,-mixed paper or rags, together with or without long fibers of vege table or animal origin and suitable for the production of a wrapping paper, sheathing, roofing felt, or of a heavy board such as may be usedfora panel board, or the like. A precipitant, such as alum or aluminum sulphate, sufiicient in amount to ensure the precipitation of rosin size or soap is then added .to the beater engine, about one-halfspart of alum to one part'of total rosincontent being suflicient to ensure such precipitation. If desired. silicate of soda may be added to the dispersion or to the stock in the beater engine, for the purpose of producing, by reaction with the aluminum sulphate, a bulky, gelatinous precipitate of aluminum silicate, which further serves to carry the dispersed particles onto the stock and envelop them so as to form additional protective coatings. The precipitation breaks down the sodium resinate, but without chemical action on the asphalt, leaving the latter to function in an unaltered state, together with the precipitated aluminum resinate which carries down therewith the dispersed asphalt particles and free rosin and effects their fixture upon the fibers, so that the stock becomes uniformly sized throughout. If desired, there may be mixed together with the dispersion, or added separately to the stock, various finely divided fillers or bulk materials in suitable amount,wood flour, cellite, kieselguhr, clay, diatomaceous earth, or the l1ke,su1'table for such purpose. The stock may then be formed into paper upon a. I ourdrinier machine provided with dryers and hot calenders, suitable for the production of wrapping paper, sheathing, roofing, or" the like. In passing through the dryers and calender-s, the paper web is heated to a temperature above the melting point of the asphalt particles, resulting in a fusion and coalescence of the particles. Such paper is highly resistant to the action of moisture, because of the high percentage of unsaponified waterproofing material contained therein relative to fibrous material and insoluble soap.

For producing a paper or board of larger. caliper, a wet or cylinder machine, so called, may be employed. In such case, the paper web is transferred from the cylinder mould to a make-up roll on which a plurality of layers or convolutions may be built up to produce a paper or board of the desiredcaliper. The board may then be stripped from the make-up roll, dried, compacted, and hot pressed or otherwise heated or calendered to effect the fusion of the asphalt particles therein. In certain instances, for the production of a multi-ply paper or board, a multi-cylinder machine may be employed. The finished boardv may be made waterproof throughout, but if desired only the. inner plies may carry asphalt therein. Or the stock may be moulded into articles which may be subjected to a temperature sufiiciently high to effect the fusion of the waterproofing material therein.

With some disadvantage, I may substitute a portion or all of the sodium resinate dispersing agent by various other soap sizes, such as fatty acid soaps produced by the saponification of a fatty acid or fatty acid ester with a suitable sodium saponifying agent. However, inasmuch as rosin soap not only functions as a dispersing agent but when precipitated produces a non-sticky soap which itself constitutes an excellent waterproofing material, I preferably use the same.

lVhile I have described the use of the dispersion as being particularly advantageous in the manufacture of a waterproof paper or paper board, it is to be understood that this use is illustrative, and that the dispersion may be employed as a waterproof binder, and for various other uses. For example, the dispersion may be uniformly incorporated into comminuted materials which maybe moulded into articles of various shapes. The shaped article during or after moulding may be baked or otherwise heated to a temperature above the fusing or melting point of the unsaponified material contained therein, to effect the permeation of the moulded structure. I

Thus, the dispersion may be uniformly admixed with comminuted fibrous material, such as sawdust, for example. The mixed mass may then be compacted, dried, and heated to effect a fusion and coalescence of the particles throughout the moulded mass.

Having thus described the nature of this invention and a way of making and using the lib Q same, although without attempting to set forth all the methods by which it may be made or all its uses,

What I claim is:

1. A processwhich comprises incorporating and uniformly disseminating-throughout a comminuted material an aqueous soapsize asphalt dispersion, drying the material, and then heating the material above the fusing point of the asphalt to cause the flowing L and coalescence of the asphalt particles within the material.

2. A process which comprises incorporating and uniformly disseminating an aqueous soap-size-asphalt disperson throughout papermaking fibrous stock, and adding a precipitant to such material, thereby effecting a precipitation and fixing of an insoluble soap and the asphalt particles on such material.

3. A process which comprises incorporat-' ing and uniformly disseminating an aqueous soap-size-asphalt dispersion throughout papermaking fibrous stock, adding a precipitant to such stock to effect the precipitation and fixture of an insoluble soap and the asphalt particles on such stock, sheeting the stock, and then drying and heating the sheeted material above the fusing point of the asphalt particles, thereby causing the fusion and coalescence of the particles within the sheet.

4. A process which comprises incorporating and uniformly disseminating an aqueous rosin-soap-asphalt dispersion throughout papermaking fibrous stock, and adding alum to such stock, thereby precipitating aluminum resinate and fixing the asphalt particles on the stock.

5. A process which comprises incorporating and uniformly disseminating an aqueous rosin-soap-asphalt dispersion throughout papermaking fibrous stock, adding alum to such stock, thereby precipitating aluminum resinate and fixing the asphalt particles on the stock, and felting the stock on a paper machine.

6. A process which comprises incorporating and uniformly disseminating an aqueous rosin-soap-asphalt dispersion throughout papermaking fibrous stock, adding alum to such stock, thereby precipitating aluminum resinate and fixing the asphalt particles on the stock, sheeting the stock, and drying and heating the sheeted material above the fusing point of the asphalt particles to cause a flowing and coalescence of the particles within the sheet.

7. A water-resistant paper product permeated with asphalt fused onto the fibers thereof and resulting from the fusion and coalescence of an aqueous soap-size-asphalt dispterslicon previously fixed to the papermaking s 00 8. A water-resistant paper product permeatedwith a high proportion of sizing material fused onto the fibers thereof, said sizing material comprising a preponderant amount of asphalt and a smaller amount. of aluminum resinate.

9. A water-resistant paper product permeated with a high proportion of sizing material fused onto the fibers thereof, said sizing material comprising a preponderant amount of asphalt and about equal quantities of aluminum resinate and free rosin.

10. A water-resistant paper product permeated with a high proportion of sizing material fused onto the fibers thereof, said sizing material comprising about 10% to 40% asphalt, based on the dry weight of fibrous material, and a smaller amount of rosin size.

11. A sized papermaking stock containing an insoluble soap size and dispersed asphalt.

12. A sized papei 'making stock containing aluminum resinate and dispersed asphalt.

13. A sized papermaking stock containing a high proportion of aluminum resinate and dispersed asphalt, said asphalt preponderating and amounting to about 10% to 40%, based on dry weight of fibrous material.

In testimony whereof I have affixed my signature.

- ALBERT L. CLAPP. 

